A slow cooker is a culinary utensil, suitable for use in the oriental cuisine and especially suitable for use in Chinese stewing cuisine generally by cooking over a slow fire. An ordinary slow cooker is composed mainly of the body of the slow cooker, a heater and the thermal insulating layer outside the main body. When it is used, the heater slowly transmits heat to the main body while the thermal insulating layer outside of the main body maintains the main body's inner temperature to allow the water inside to be slowly heated for a sustained period of time so that food inside can be well stewed.
Prior art slow cookers mostly consist of a lid, a porcelain container (the main body), an inner casing (heat transmission medium), a heater, a shell (thermal insulating layer) and a pedestal. The porcelain container is in the innermost space, and the inner casing with a heater and the shell are one after another in the outer space of the porcelain container. The porcelain container is covered with a lid. When used, the heater transmits heat to the porcelain container so that food inside can be heated.
The prior art slow cooker has the following shortcomings: First, there is air in the gap between the shell and the inner casing. Since air does not possess superb heat-proof quality, a large amount of heat is transmitted through the air to the shell, and by heat radiation to the shell, and further to the outside air, which results in a high temperature of the shell and a huge loss of heat thereby having poor warmth-keeping effects.
Second, there is a gap of 2-4 mm between the inner casing and the porcelain container, which reduces heat conduction from the inner casing to the porcelain container.